package binarysearchtree;

public class BinarySearchTree {


    public TreeNode root = null;

    public TreeNode search(int key) {
        TreeNode cur = root;
        while (cur != null) {
            if(cur.val < key) {
                cur = cur.right;
            }else if(cur.val > key) {
                cur = cur.left;
            }else {
                return cur;
            }
        }
        return null;
    }

    public void insert(int val) {
        TreeNode node = new TreeNode(val);
        if(root == null) {
            root = node;
            return;
        }
        TreeNode cur = root;
        TreeNode parent = null;
        while (cur != null) {
            if(cur.val < val) {
                parent = cur;
                cur = cur.right;

            }else if(cur.val > val) {
                parent = cur;
                cur = cur.left;
            }else {
                return;
            }
        }
        //parent 指向的节点 就是 需要插入的节点位置 的 父亲节点
        if(parent.val > val) {
            parent.left = node;
            
        }else {
            parent.right = node;
        }
    }


    //key = 10;
    public void remove(int key) {
        TreeNode parent = null;
        TreeNode cur = root;
        while (cur != null) {
            if(cur.val < key) {
                parent = cur;
                cur = cur.right;
            }else if(cur.val > key) {
                parent = cur ;
                cur = cur.left;
            }else {
                removeNode(parent,cur);
                return;
            }
        }
    }
    private void removeNode(TreeNode parent,TreeNode cur) {
        if(cur.left == null) {
            if(cur == root) {
                root = cur.right;
            }else if(cur == parent.left) {
                parent.left = cur.right;
            }else {
                parent.right = cur.right;
            }
        }else if(cur.right == null) {
            if(cur == root) {
                root = cur.left;
            }if(cur == parent.left) {
                parent.left = cur.left;
            }else {
                parent.right = cur.left;
            }
        }else {
            TreeNode target = cur.right;
            TreeNode targetP = cur;
            while (target.left != null) {
                targetP = target;
                target = target.left;
            }
            cur.val = target.val;
            if(target == targetP.left) {
                targetP.left = target.right;
            }else {
                targetP.right = target.right;
            }
        }
    }
}


 class TreeNode {
    public int val;
    public TreeNode left;
    public TreeNode right;

    public TreeNode(int val) {
        this.val = val;
    }
}



